1. Field of the Invention
The present invention relates to a resin sealing method and apparatus for a semiconductor device. More particularly, the invention relates to a resin sealing method and apparatus which are well adaptable for the resin sealing of a semiconductor device having an underfill structure, e.g., a semiconductor device including a flip-chip connected semiconductor chip.
2. Description of the Related Art
A semiconductor device having a semiconductor chip mounted by a flip chip method is shown in FIG. 16. As shown, a semiconductor chip 12 is flip-chip connected onto a substrate 10, and then a joining portion between the semiconductor chip 12 and the substrate 10 is filled with sealing resin 14, to thereby seal the joining portion by resin. The sealing resin 14 functions to protect the joining portion between the semiconductor chip 12 and the substrate 10 and to relieve a thermal stress caused by the thermal coefficient difference of expansion between the substrate 10 and the semiconductor chip 12.
A known method of filling the joining portion with resin 14, generally used, is shown in FIG. 17. As shown, the substrate 10 is slantly supported, and in this state, sealing resin 14 is allowed to flow into the joining portion between the substrate 10 and the semiconductor chip 12. A number of solder bumps 16 are studded on the joining portion between the substrate 10 and the semiconductor chip 12. The sealing resin 14 flows through gaps among those bumps 16. To make the flow of the sealing resin easy, the substrate 10 is slanted, and the sealing resin 14 flows onto the slanted substrate 10 while expelling air from the joining portion.
When the sealing resin 14 is allowed to merely flow into the joining portion of the flip-chip connected semiconductor chip 12 to fill out there, the sealing resin 14 imperfectly fills the joining portion between the semiconductor chip 12, and sometimes the substrate 10 and air bubbles are left in the gap portion. Actually, the width of the joining portion (between the semiconductor chip 12 and the substrate 10) is about 0.1 mm, and recently it is reduced from 0.1 mm to 0.02 mm to 0.03 mm, extremely narrow. A number of solder bumps 16 are studded in the joining portion, and those bumps restrict the flow of the sealing resin 14. When the filler-contained resin is used, the resin flow is further impeded. Therefore, the method of merely flowing the sealing resin 14 into the underfilled portion cannot achieve the reliable sealing. A resin hardening time in the potting process is longer than in the transfer molding process. Therefore, also in the work efficiency, the method by merely flowing the sealing resin 14 into the underfilled portion is not preferable.
The solder bumps are minutely different in height and the semiconductor chips are also minutely different in thickness with the pieces to be molded. Therefore, when the transfer molding is used for sealing flip-chip connected semiconductor chip by resin, the following disadvantages are present: 1) a thin layer of resin will be formed on the outer surface of the semiconductor chip; and 2) the resin excessively presses the molded piece to possibly break the molded piece. Further, the resin material including extremely small silica particles or not including the same must be used since the gaps in the underfilled portion are extremely small. Such a resin material is easy to enter the gaps. Therefore, if the clamping of the molded piece is not properly, the resin will enter the gaps to form resin flash. The same disadvantageous phenomenon occurs also when the semiconductor chip is minutely displaced (when viewed in plan) on the substrate. For this reason, it is almost impossible to resin seal the underfilled portion resulting from the flip-chip connection by the conventional transfer molding process.
Accordingly, an object of the present invention is to provide a resin sealing method for sealing a semiconductor device with resin which is improved such that a transfer molding process is used for manufacturing a semiconductor device having an underfill structure, e.g., a semiconductor device including a flip-chip connected semiconductor chip, and the use of the transfer molding process provides a reliable underfilling free from air bubbles and produces a reliable semiconductor device, and an efficient underfilling process is provided.
Another object of the invention is to provide a resin sealing apparatus achieving the same improvements as by the resin sealing method.
To achieve the above object, the present invention has the following constructions:
A resin sealing method for a semiconductor device for sealing a molded piece including a semiconductor chip with resin by a transfer molding process in a state that the molded piece is clamped by a mold, the method comprises the steps of:
covering a clamping surface of the mold for clamping the molded piece and sealing resin material with a release film;
clamping the molded piece and sealing resin material with the release film placed therebetween, and clamping the resin material through an urging means for urging the resin material in the mold closing direction; and
feeding molten resin to the molded piece under pressure by the urging force of the urging means, thereby filling the molded piece with the resin material.
In the resin sealing method, the resin material takes the form of a cylindrical resin tablet, and the resin tablet is placed while being laid down on the clamping surface of the mold, whereby the resin filling is performed.
A resin sealing apparatus for a semiconductor device for sealing a molded piece including a semiconductor chip with resin by a transfer molding process in a state that the molded piece and sealing resin material are clamped by a mold, through a release film covering a clamping surface of the mold, the resin sealing apparatus is characterized in that a mold portion of the mold for clamping the resin material is supported movably in the mold opening and closing directions, and urged in the mold closing direction by an urging means so as to be able to feed molten resin under pressure.
In the resin sealing apparatus, the surface of the mold portion for pressing the resin material is arcuately curved inward in cross section, the resin material being laid down on the surface of the mold portion.
Further, the mold portion is a cull insert with a spring as the urging means, and a center block is fixed at a location opposed to the cull insert.
A resin sealing method for sealing a joining portion between a semiconductor chip and a substrate by feeding pressurized sealing resin to an underfilled portion of a molded piece in which a semiconductor chip is mounted on a-substrate, thereby sealing the joining portion, the method is characterized in that when the molded piece is clamped with a mold, the perimeter of the underfilled portion, except a portion to which a gate continuous to the underfilled portion is connected, is closed with a release film, and in a state that the perimeter of the underfilled portion is closed, the sealing resin is fed under pressure to the underfilled portion, to thereby fill the underfilled portion.
In the resin sealing method, when the underfilled portion is closed by the release film, the film is pressed against the side face of the semiconductor chip, whereby only the interior of the underfilled portion is filled with the sealing resin.
Further, when the underfilled portion is closed by the release film, the film is pressed against the side face of the semiconductor chip, through an elastic member elastically deformable when it receives a clamping force for clamping the molded piece.
When the underfilled portion is closed by the release film, the sealing resin fills out side-face sealing portions provided between the side faces of the semiconductor chip. and the release film, and the underfilled portion.
When the underfilled portion is filled with the sealing resin, the side face of the semiconductor chip to which the gate is to be connected and the side face thereof opposed to and parallel to the gate-connecting side face are both closed by the release film.
When the underfilled portion is filled with the sealing resin, a pulsative motion is applied to the sealing resin.
A resin sealing apparatus for a semiconductor device in which a molded piece having a semiconductor chip carried on a substrate is clamped with the top half and the bottom half of a mold, and pressurized sealing resin is fed to an underfilled portion of the molded piece, thereby filling out the underfilled portion, the apparatus is characterized in that the semiconductor chip is located on the top half or the bottom half, and a cavity recess is provided for closing the side faces of the molded piece, except the side face thereof including the end of a gate continuous to the underfilled portion, are closed by use of a release film.
In the resin sealing apparatus, an elastic member is provided on side surface of the cavity recess, when the molded piece is clamped, the elastic member is elastically deformed by a clamping force produced to press the release film against the side face of the semiconductor chip.
Further, the resin sealing apparatus further comprises pulsating means for pulsating the sealing resin when the pressurized sealing resin is fed to the underfilled portion.